Gravity-type pipe conveyance systems for waste or storm water generally include a mainline pipe or conduit to which service lateral pipes are connected. Many applications call for the connection of the lateral pipes to be made such that the lateral is perpendicular to the mainline pipe. Such service connections are often referred to as “Tee” connections. Alternatively, the service lateral pipe can be connected at an angle (although with the long axis of the lateral preferably always intersecting the long axis of the mainline pipe) and is thus designated, for example, as a “Wye” or 45-Degree service connection.
Service connections often require a hole to be cored through the sidewall of the mainline pipe. The diameter of the cored hole is made slightly larger than the diameter of the service lateral pipe, which has a smaller diameter than the mainline pipe.
One effective service connection system is available from Inserta Fittings Inc., the assignee of the present application (www.insertatee.com), and marketed under the trademark INSERTA FITTINGS. That system comprises a three-piece service connection that is compression fit, without special tooling, into the hole that is cored through the sidewall of a wastewater or storm water mainline pipe. The three-piece service connection comprises a substantially rigid, cylindrical, hollow hub; an elastomeric sleeve; and a stainless steel band. The sleeve fits into a cored hole in the mainline pipe. A leading end of the hub is forcibly inserted into the elastomeric sleeve. After the hub is inserted, a stainless steel band is fastened around the sleeve to secure together the sleeve and the hub. The exposed or trailing end of the hub can be shaped to define a conventional bell component of a bell and spigot joint, and receives the spigot end of the service lateral that is to be connected. This type of service connection may be used with any of a wide variety of pipe types (concrete, PVC, corrugated, ribbed, etc).
A coring tool is used for coring the requisite hole in the mainline pipe. A coring tool generally includes a hollow, cylindrical hole saw that is mounted to an arbor. The leading end of the arbor comprises a pilot shaft, normally configured as a drill bit, that is centered in the hole saw. The other end of the arbor is mounted to a drill motor or the like for powering rotation of the hole saw to cut through the pipe.
It is important that the coring tool is properly aligned with the mainline pipe to produce a hole that is correctly formed, such that the central axis of the hole intersects the central axis of the mainline pipe. Put another way, the coring tool must remain securely aligned as the hole saw is advanced through the pipe sidewall. If the tool and resulting hole are not properly aligned, the central axis of the hole will not intersect the long axis of the mainline pipe. Consequently, the misaligned hole made in the sidewall of the mainline pipe will be oblong rather than circular. This can result in attendant misalignment of the service connection with the mainline pipe, hence misalignment of the service lateral, which can lead to leaking and eventual structural failure of the connection.
It is possible for an installer to apply excessive axial force on the service lateral pipe when fitting the spigot end of that pipe into the connection hub. In such an instance, and especially where the cored hole is not quite circular, the excessive force may cause an undesirable amount of penetration of the sleeved end of the hub into the mainline pipe, which can result in interference with the operation and/or inspection of the mainline pipe.
There exists in the prior art complicated tools for engaging a mainline pipe to secure a platform or guide apparatus on a pipe for controlled movement of a connected coring device to form the hole in the pipe sidewall. Such complicated devices usually require many parts and are cumbersome, especially in an environment where a lateral connection is made to, for example, an existing main sewer line that has been exposed, in place, several feet underground. Usually, only a narrow trench is provided for a worker to access the main and make the connection. Moreover, in some construction environments, rainwater, mud, debris, and other elements may make it extremely difficult and/or time consuming for a worker to use conventional mechanisms for controlling coring tools to produce a properly formed hole.
The complexity of engaging a mainline pipe to secure a guide thereto for controlled movement of a connected coring device is increased when the mainline pipe includes outwardly protruding features such as spaced-apart ribs. Such ribs are sometimes attached or integrally formed with the pipe to enhance the pipe's resistance to crushing failure.
The present invention is directed to a compact and elegantly simplified assembly for aligning a coring tool to cut a precisely formed hole in a pipe sidewall. Embodiments are described for using the assembly with pipes having various sidewall surface features, including ribbed sidewalls. Other advantages and aspects of this invention will become clear upon review of the following description and drawings.